Controls for dewatering press



Oct. 4, 1966 A. H. BURNER ET AL 3,276,353

CONTROLS FOR DEWATERING PRESS 2 Sheets-Sheet 1 Filed July 2l, 1965 Oct. 4, 1966 A. H, BURNER ET A1. 3,276,353 CONTROLS FOR DEWATERING PRESS Filed July 2l, 1965 2 Sheets-Sheet 2 FIG -4 I NVENTORS ANDRE H. BURNER 8 BY ALAN D. GRAHAM ATTORNEYS United States Patent Oiice 3,276,353 Patented Oct. 4, 1966 3,276,353 CONTROLS FOR DEWATERING PRESS Andre H. Burner and Alan D. Graham, both of Piqua,

Ohio, assignors to The French Oil Mill Machinery Company, Piqua, Ohio, a corporation of Ohio Filed July 21, 1965, Ser. No. 477,350 Claims. `(Cl. 100-37) This application is a continuation-in-part of application Serial No. 264,165, filed March 1l, 1963, now abandoned, and relates to screw presses and the like used for removing moisture such as water from various materials, and particularly to controls for such a press for preventing dama-ge due to over-heating of the material.

In continuous processes wherein liquid is removed from material by means of a screw extruder such as a screw press, the moisture or liquid content of the material as rst supplied to the press may vary somewhat. As is known in the art, the material is subjected to substantial mechanical pressure and to mechanical working in the press, and suitable small drainage openings in the walls of the press permit the expressed liquids to separate from the materials and be removed. If for some reason the moisture content of the incoming material is decreased substantially, it is a possibility that the material may be essentially dry before it reaches the outlet of the screw press.

In such a case, with the material still being subjected to high mechanical pressures in the order of several thousand p.s.i., the frictional heating of the material may cause the material to be scorched or burned, and the material may -thus 'be d-amaged to such an extent that it is no lon-ger useful. One example of such a situation is in the drying of synthetic or natural latex materials which cannot withstand heating above temperatures in the range of 250 to 400 F., depending upon the polymer.

Of course, the basic function of the screw press is to remove moisture from the material being processed. As stated previously, the process can proceed within the press, for example where the initial moisture content of the material fluctuates and may sometimes be relatively low, to the point where essentially all moisture is removed from the material and the heat of friction rises to an undesired temperature. Taking the case of synthetic latex material as .an example, every pound of moisture present in the material requires 980 B.t.u. to remove it. This is, of course, the heat required to vaporize this pound of moisture and thereby cause it to separate from the material as water vapor. It has been determined from actual operation, therefore, that addition of moisture, in the form of liquid added to the material entering the press, will require that much more heat of friction to be absorbed in the action of vaporizing such moisture, and that the ultimate temperature of the material, where it tends to reach its maximum adjacent the outlet of the press, will be lowered accordingly. As a result, by correlating the .amount of moisture added to the material at the inlet with the temperature of the material adjacent the outlet of the press, this temperature can be controlled and maintained within desired limits.

Accordingly, the present invention has as its principal object a novel control in combination with screw presses, particularly as used for dewatering or drying, whereby the temperature of the material in `the press adjacent its outlet is controlled by controlling the moisture content of material being supplied into the press for processing.

Another object of the invention is to provide a novel process for controlling the temperature of material in a screw press by controlling the amount of moisture in the material being processed before such material enters the press.

Another object of the invention is to provide in combination with .a dewatering or drying screw press a control system including a temperature sensing element arranged to sense the temperature of material adjacent the outlet of the press, an automatic controller responding t0 changes in temperature indicated 'by said sensing element, and a pipe or similar conduit leading from a supply of suitable liquid such as water to a spray nozzle which is directed on the material being `supplied to the inlet of the press, together with a valve in such conduit and governed by the controller to adjust the amount of water sprayed onto the material in accordance with the temperature of the material at the press outlet.

Still another object of the invention is to provide a c-ontrol system for two successively connected extruders or screw presses wherein a temperature sensing element is arranged to sense the temperature of material adjacent the outlet of the second press `and is adapted to control automatically the moisture content of the material discharged from the rst press to prevent an excessive temperature of the m-aterial processed within the second press by using excess heat to vaporize additional moisture.

It is also an object of the invention to provide a control system as outlined above wherein `the discharge cone of the first dewatering press is adjusted automatically in response to changes in temperature adjacent the discharge of the second drier press to prevent over-heating of the material being processed.

Another object of the invention is to provide for addition of moisture to material discharging from the press in a suliicient regulated amount to avoid temporary overheating of the material.

Other objects `and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings:

FIG. l is a diagram illustrating the manner in which the present control is applied to a dewatering and drying system incorporating continuous flow of material through one or more screw presses;

FIG. 2 is a view, partly Ibroken away and in section, of a typical variable control valve used in the system;

FIG. 3 is a partial sectional view on an enlarged scale, through the discharge cone of the second press shown in FIG. l;

FIG. 4 is an enlarged section view of the discharge end of the dewatering press; and

FIG. 5 is a fragmentary end view of the discharge end of the dewatering press.

Referring to the drawings, which shows a preferred embodiment of the invention, a typical system is shown wherein a first expressing or dewatering screw press 10 is arranged to receive material, such as synthetic latex in crumb form, from a vibrating screen conveyor 12, of conventional construction.

The crumb latex is supplied` o) from a processing tank 14, in which the crumb is formed by known processes, and it is supplied to the vibrating screen conveyor where liquid is drained away by gravity as much as possible. The material is then fed into the feed hopper of the press 10.

Details of construction of such a press are shown in copending application Serial No. 92,909, filed March 12, 1961, now abandoned which is assigned to the same assignee of this application. It will be understood that the shaft of the press is rotated through a gear reduction drive 17 which receives power input from a suitable electric motor 18. The gear drive may also provide rotary power for a shredder 20, such as disclosed in copending application Serial No. 264,302, led March 1l, 1963, now abandoned, and rotation of the press shaft 22 will cause the several screw ilights 23 mounted thereon to force the material past breaker lugs 24 and over collar 25 which are mounted on the shaft opposite the breaker lugs. Other types of screw presses are also within the scope of the present invention, and the ones shown are merely exemplary.

The resultant pressure on the material will express the encapsulated liquids therefrom, and the action of the press on the material will tend to tear the crumb material and rupture the small pockets of encapsulated liquids. In addition, due to the pressure exerted on the material and the twisting and tearing of the parts, substantial heat of friction will be generated and tend to vaporize the encapsulated liquids to promote further the removal of such liquids. The press cage is of conventional construction and is provided with small drainage openings (not shown) such as is well known in the screw press art for the purpose of carrying away the expressed liquids.

The dewatered material then passes through the shredder and drops into a chute or tube 30 which is connected to the inlet hopper 32 of a drying press 35. This press is of the same general construction as the press 10, although it may have drainage openings only in the first or left-hand section thereof, or in some instances no drainage openings at all in which event it is an extruder only and not an expressing press. The body ofthe press preferably is covered with suitable hoods 37 which are provided with vent ducts 38 leading to outside the building in which the apparatus is housed, so as to carry away any vapors which may result from the drying process. In other respects, the press is essentially of the same construction as the press 10, and thus it includes a drive motor 18a, a gear drive unit 17a, and a shredder 20a into which the dried crumb material passes from the outlet of the press.

Adjacent the discharge end of the press there is a temperature sensing transducer in the form of a thermocouple 40 and this thermocouple is wired, as indicated at 42 to a recorder-controller 45 which is in turn connected as is shown at 47 to a variable control valve 50. Any suitable type of thermocouple, controller and valve may be used.

In practice a thermocouple available from Foxboro Instrument Company, under the trademark MINOX has been used and found suitable. Preferably, the controller is of the recording type and thus provides a record of its function on a time basis. A suitable controller for this purpose is a model M/40 controller'available from Foxboro Instrument Company. This controller in Iturn is connected to govern the operation of the variable control valve 50 (shown on a larger scale and partly in section in FIG. 2) which likewise is of conventional construction and may be, for example, a type V4 control valve also available from Foxboro Instrument Company.

It should be understood that the temperature senser, they recorder-controller, and the control valve are all commercially available items which are known to those skilled in the art, and the types mentioned in the foregoing description are merely illustrative of suitable types for the purpose. f'

The valve 50 controls flow of water or other suitable liquid from a suitable source (not shown) through a pipe 52 which terminates in a spray nozzle 55 directed to discharge the water owing through the pipe onto the material falling from the shredder 20 into the tube or duct 30.

Thus, the arrangement is such that if the temperature of material at the discharge end of the drier press 35 in the vicinity of thermocouple 40, tends to rise then the controller 45 will cause valve 50 to open and increase the supply of water which is added to .the crumb material passing to the press 35. In this manner the temperature of the material at the outlet of press 50 can be effectively controlled (as previously explained) to maintain such temperature within predetermined limits and particularly below a temperature at which the crumb material might be damaged.

The dried crumb material from shredder 20a falls into an outlet to 60 which leads to the conduit 62 of an air conveyor, and a ow of air into this tube, as from the blower 63, will carry the crumb material to a baling machine, or to any other suitable point of storage.

Due to the construction of the above-described moisture controlling apparatus, there will be some time lag between the time that the temperature is sensed by the thermocouple 40 and the recorder-controller 45 acts to open valve 50 and add some moisture to the material passing into the chute 30. As a result, under some circumstances the temperature of the material discharging from the press 35 may continue to rise for a time. The present invention also provides for an immediate cooling of the material discharging from the press 35 if the temperature of the material rises to a certain predetermined point, for example close to the temperature at which this material might be damaged.

For this purpose, one or more spray nozzles, one of which is shown at in FIG. 3, may be mounted in the discharge cone member 67 of press 35, arranged to spray cooling liquid such as water onto the material discharging toward the shredder 20. Liquid is supplied to this nozzle from a flexible tube 68 (for accommodating adjusting movement of the cone 67) and this tube in turn is connected t-o a supply pipe 70. A control valve 72 is connected -in line '70 and receives cooling liquid from the supply pipe 52 upstream of valve 50. The valve 72 is in turn controlled, via the conventional control connection 73, by the recorder-controller 45. The adaption of recorder-controller units to 'the separate operation of two or more valves is well known, and hence details of such an arrangement are not supplied herein.

The arrangement is such that if the recorder-controller receives a signal from thermocouple 40 indicating a temperature a-t or above a predetermined level, valve 72 will open in addition to valve 50, and the valve 72 will remain open until the temperature drops to below this predetermined level, at which time this valve will be s'hut. The drop in temperature will result from the addition of moisture at the inlet through the spray nozzle 55, whereby the material entering the press 35 will contain more moisture and thus require the absorption of more heat to remove this moisture. It will be appreciated therefore t-hat valve 72 may close at a higher temperature, and substantially before, the valve 50 while the latter may be varied and may continue to supply liquid to the spray nozzle 55.

When the temperature of the material at the discharge of press 35 has risen to the higher level at which valve 72 is opened, the liquid sprayed through fthe nozzle 65 will contact the hot material and will flash off almost instantaneously, thereby cooling the material to a temperature below which it would be damaged.

Accordingly, the present invention provides a novel method for preventing over-heating and possible darnaging of materials from which moisture is being removed in a continuous screw press. The preferred arrangement, as illustrated and described, embodies automatic temperature sensing transducers, such as a thermocouple, and controls operating therefrom to adjust the addition of liquid to the incoming material automatically. It should be understood, however, that the process can be performed elfectively by manual manipulation of the amount of liquid being added to the material entering the press or discharging from it, for example by opening and closing valves by hand, while referring to the temperature of the material within the press. For example, such yreference could be obtained from a simple thermometer providing visual indication of the temperature of the material adjacent the discharge end of the press. It will be clear, therefore, that the process is not limited to the particular form of apparatus disclosed and described herein.

Referring to another embodiment of the present invention, as shown in detail in FIGS. 4 and 5, the discharge cone 67 of the dewatering screw press 10 is carried by an annular gear member 75 and is adjusted axially by rotation of the gear member 75 which has a threaded connection 77 with the stationary frame member 79. This well-known adjustment of the discharge cone 67 is adapted to vairy the annular discharge oriice 80 defined lbetween the inside surface of the cone 67 and the outside surface of the final discharge sleeve 82 mounted on the press shaft 22.

The rotation of the gear member 75 and thus adjustment of the cone 67 is `operated through a worm gear 85 (FIG. 5) in engagement with the teeth 86 formed on the gear member 75 and is driven by a reversible electric motor 88 through a suitable gear drive unit 90. The motor 88 is connected by the leads 92 to a recordercontroller 95 which, in turn, is connected by the leads 42 to the thermocouple 40 (FIG. l). In this embodiment, instead of adding liquid through the conduit 52 to the material discharged from the screw press 10, the moisture within the material as discharged from the screw press is controlled automatically by adjusting the discharge cone 67 to vary the internal expressing pressure within the press 10.

When the temperature sensing element 4l) senses an increase in the temperature within the material adjacent the discharge end within the drying press 35, the controller 95 energizes the motor 88 causing it to adjust the discharge cone 67 correspondingly so that the annular oriiice 80 is increased which results in reducing the expressing pressure within the screw press 10. Thus, the material discharged from the press 10 will contain a higher amount Iof moisture which, in turn, will result in reducing temperature within the drying press 35 in the same manner as described above when liquid is added through the conduit 52 to the material entering the inlet of the drying press 35. That is, additional moisture in the press 35 absorbs heat from the material to vaporize the moisture.

While the method and forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made `therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A control system for governing the temperature and therefore the moisture of material being processed in an extruder which removes moisture from material and which causes friction heating of the material, said control including a transducer mounted to sense the temperature of material being processed within the extruders, a controller operated by said transducer, means including a uid supply lconduit arranged to add fluid to material entering the extruder, and an automatically adjustable valve controlling flow through said conduit and having an operating connection from said controller to adjust said valve for increasing and decreasing the amount of fluid added to the material in direct relation to an increase and decrease in temperature sensed by said transducer to avoid excessive heating of the material after substantially complete removable of moisture therefrom.

2. A control system for governing the temperature of material being processed in a continuously operating extruder Which removes moisture from material and which causes yfriction heating of the material, said control including a transducer mounted to sense the temperature of material adjacent the discharge end of the extruder where heating of the material tends to be greatest, a controller operated by said transducer, means including a liquid supply conduit arranged to add liquid to material entering the extruder for increasing the moisture content of the material entering the extruder, and an automatically operable variable orifice valve in said conduit and having an operating connection from said controller arranged to adjust said valve in an opening direction to increase the amount of liquid added to the material entering the extruder in response to an increase in temperature sensed by said transducer, said controller for said valve being correlated to increase the amount of liquid added -by an amount sufficient to prevent overheating of the material within the extruder due to excessive heating of material after substantially complete removal of moisture therefrom.

3. In combination with a screw press having a press chamber and a rotatably driven screw extending through said chamber, means forming inlet and outlet openings at opposite ends of said chamber through which material enters the chamber for expression of liquids therefrom and through which the material exits from the press after having liquid expressed therefrom, means for controlling the temperature of the material being processed in said press comprising -a temperature sensing transducer mounted adjacent said outlet opening of said press to sense the temperature of the material in said press adjacent said outlet and arranged to transmit a signal accordingly, means for supplying a controlled flow of Huid into the material passing into said press inlet including an automatically adjustable valve for varying the iiow of such liquid, and a controller connected to be operative on response to signals from said transducer and connected to control said valve for varying the valve opening in response to a change in the temperature of the material adjacent said press outlet.

4. In combination with a screw press -having a press chamber and a rotatably driven screw extending through said chamber, means forming inlet and outlet openings at opposite ends of said chamber through which material enters the chamber for expression of liquids therefrom and through which the material exits from the press after having liquid expressed therefrom, means yforacontrolling the temperature of the the material lbeing processed in said press comprising a temperature sensing transducer mounted adjacent said outlet of said press to sense the temperature of the material in said press adjacent said outlet and arranged to transmit a signal accordingly, a controller connected to be operative in response to signals from said transducer, means for supplying a controlled flow of liquid into the material passing into said press inlet including an automatically adjustable valve for varying the iiow of such liquid, and an operative connection between said controller and said valve for varying the valve opening to increase the flow of liquid to the material in response to an increase in the temperature of the material adjacent said press outlet.

5. A control system for governing the temperature of material being processed in a continuously operating extruder, said extruder having means defining an inlet and a discharge opening through which the material is received and through which the dried material is discharged respectively; said control comprising a transducer mounted to sense the temperature of material adjacent said discharge opening of said extruder where heating of the material tends to be greatest, a controller operated by said transducer, means including a liquid supply conduit arranged to add liquid to material passing to said inlet opening of said extruder for increasing the moisture content of the material entering the extruder, an automatically operable variable orifice valve in said conduit and having an operating connection from said controller arranged to open said valve and increase the amount of liquid Iadded to the material in response to an increase in temperature sensed by said transducer, a separate liquid supply connection terminating in means arranged to spray liquid onto material passing from said discharge opening f said extruder, a second automatically operable valve in said separate liquid supply connection, and means connecting said controller to said second valve for opening said second valve in response to a predetermined temperature sensed by said transducer.

6. An apparatus fior continuously drying material and fior maintaining the temperature of the material under a predetermined 4maximum limit by using rictional heat to vaporize additional moisture, said apparatus comprising an extnuder having means defining an inlet and a discharge opening through which the material is received and through which the ldried material is discharged respectively, a transducer mounted within the extruder to sense the temperature of material adjacent said discharge opening where heating of the material tends to be greatest, means or increasing the moisture content of the material, and a controller operated by said transducer and connected to operate automatically said means for increasing the moisture in response to an increase in temperature adjacent said discharge opening.

7. An apparatus as defined in claim 6 in which the means for increasing the moisture content provides for adding moisture at the inlet opening of the extruder.

8. An rappauatus as defined in claim 6 in which the means for increasing the moisture content provides for adding moisture to the material after it leaves the discharge opening of the extruder.

9. A control :system tor governing the temperature of material being processed in a continuously operating dryer extruder having means defining Ian inlet opening adapted to receive material discharged from an extruder and also having means defining a discharge opening through which dried material is discharged, said system comprising an adjustable annular discharge member on the discharge end of .said expressing extruder for defining an adjustable orifice to control the internal pressure within said expressing extruder, a power operated reversible drive means for adjustably positioning said discharge member, a transducer mounted to sen-se the temperature of moisture adjacent said discharge opening of the dryer extruder where heating of the material tends to be greatest, a controller operatively connected to said transducer and to said drive means or automatically adjusting said discharge membe-r to control the amount of moisture in the material entering said inlet opening of the dryer extruder by controlling the amount of moisture in the material discharged from the extruder.

10. An apparauts for continuously drying material and or maintaining the temperature of the material under a predetermined maximum limit by using frictional heat to vaporize additional moisture, said apparatus comprising first and second screw presses having corresponding inlet and discharge openings and arranged so that the material discharged from the first press enters the inlet of the second press, an adjustable discharge member on said first press for varying the size of the discharge opening to control the expressing pressure within said first press and thus the amount of moisture removed thereby, a reversible drive motor adapted to position said discharge member, a transducer mounted to sense the temperature of material adjacent the discharge opening of the second press where heating of the material tends to be greatest, a controller operated by said transducer, and means for operatively connecting said controller to said drive motor so that an increase in temperature in said second press actuates said drive motor through said controller and provides a corresponding adjustment of said discharge member to increase the size of said discharge opening of said first press and thereby increase the amount of moisture in the material discharged from .said first press.

1l. A process for continuously drying material by subjecting said material to mechanical working in a continuous extruder and for preventing overheating of the material, said process comprising the steps of sensing the temperature of material within the extruder adjacent the discharge end of the extruder where heating of the material tends to be greatest, and controlling the amount of moisture in the material in relation to the temperature sensed to increase the amount of moisture when .such temperature increases whereby heat available to vaporize such additional moisture will be derived from the material so that the temperature of the material -as discharged from the extruder will be lowered.

12. A process for continuously and successively drying material by subjecting said material to mechanical pressure in a series of first and second connecting extruders and for maintaining the temperature of the material under a predetermined maximum limit by using friction heat to vaporize additional moisture, said process comprising the steps of sensing the temperature of material within the second extruder adjacent the discharge end where heating of the material tends to be greatest, increasing the amount of moisture in the material discharged from said i'st extruder when such temperature increases so that heat available to vaporize such additional moisture will be derived from the material and will thereby lower the temperature of the material, and correspondingly decreasing the amount of moisture in material entering the second extruder in response to reduction of the temperature of the material to a predetermined minimum temperature.

13. A process for continuously and successively drying material by `subjecting said material to mechanical pressure in a series of first .and second connecting screw presses and for maintaining the temperature of the material under a predetermined maximum limit by using friction heat to vaporize additional moisture, said process comprising the steps of compressing the material in said screw press to express moisture therefrom, sensing the temperature of material within the second screw press adjacent the discharge end where heating of the material tends to be greatest, and controlling the amount of moisture retained in the material discharged from said first press in response to the temperature sensed in said second press so as to increase the amount of moisture retained when .such temperature increases so that heat available to vaporize such additional moisture will be derived fromv the material and will thereby lower the temperature of the material, and correspondingly [decreasing the amount of moisture retained in the material discharged from the first press in response to reduction of the temperature of the material to a predetermined minimum temperature.

14. A continuous process for removing moisture from material by subjecting said material to mechanical pressure in la continuous extruder with resultant expression of the moisture from the material and frictional heating of the material, said process comprising the `steps of `adding moisture to the material being supplied to the extruder for processing, and controlling the addition of moisture to the material with reference to the temperature which the material reaches within the extruder by increasing the amount of moisture added When such temperature increases whereby the heat required to remove such -additional moisture will be derived from the material and will thereby lower the maximum temperature to which the mate-rial Iis raised.

1S. A continuous process for removing moisture from material by subjecting said material to mechanical piressu're in a continuous extruder With resultant expression of the moisture from the material and frictional heating of the material, said processes comprising the steps of adding liquid to the material being supplied to the eX- truder for processing so as to` increase the amount of moisture :available to be removed, `and controlling the addition of moisture material with reference to the tem penature which the material reaches Within the extruder by increasing the amount of moisture added when such temperature increases whereby heat available to vaporize such additional liquid will be derived from the material and will thereby lower the maximum temperature to which the material is raised.

References Cited by the Examiner UNITED STATES PATENTS 1,579,914 4/1926 Chalmers 241--33 X 1,813,086 7/1931 Sahmel 241-33 2,340,009 1/1944 Meakin 100-43 2,355,091 8/1944 McDonald 100-73 X 8/1961 Zies 100-74 FOREIGN PATENTS 905,612 9/1962 Great Britain.

LOUIS O. MAASSEL, Primary Examiner. 

11. A PROCESS FOR CONTINUOUSLY DRIVING MATERIAL BY SUBJECTING SAID MATERIAL TO MECHANICAL WORKING IN A CONTINUOUS EXTRUDER AND FOR PREVENTING OVERHEATING OF THE MATERIAL, SAID PROCESS COMPRISING THE STEPS OF SENSING THE TEMPERATURE OF MATERIAL WITHIN THE EXTRUDER ADJACENT THE DISCHARGE END OF THE EXTRUDER WHERE HEATING OF THE MATERIAL TENDS TO BE GREATEST, AND CONTROLLING THE AMOUNT OF MOISTURE IN THE MATERIAL IN RELATION TO THE TEMPERATURE SENSED TO INCREASE THE AMOUNT OF MOISTURE WHEN SUCH TEMPERATURE INCREASES WHEREBY HEAT AVAILABLE TO VAPORIZE SUCH ADDITIONAL MOISTURE WILL BE DERIVED FROM THE MATERIAL SO THAT THE TEMPERATURE OF THE MATERIAL AS DISCHARGED FROM THE EXTRUDER WILL BE LOWERED. 